The present invention relates to the testing of cellular networks, and in particular to controlling the load in cellular networks for test purposes.
The performance in a mobile telephone network is highly dependent on the traffic load of the system. A high traffic load leads to interference in the system, reducing the performance of the system. In a cellular system, in which signals are received and transmitted through the air interface, it is impossible to control the traffic load, that is, the number of people calling and the location of the mobile terminals.
The optimization of a mobile network is usually done by trying different parameter settings. This may involve the testing of several hundred parameters. The parameter setting that generated the best result in terms of dropped calls, handover performance etc. is then used. Often, the traffic load changes from test case to test case and it is often difficult to determine if a change in performance was caused by the new test case or by fluctuations in traffic load. This means that the parameters are set according to a combination of test results and guesswork.
When increasing the number of subscribers in a network it is necessary to decide on a maximum load in the network. There is no way today of determining the maximum load that can be handled by a network, that is, the maximum number of subscribers that can be accepted in a given network, or when it is necessary to increase the capacity of the network.
It is an object of the present invention to enable the control of the traffic load and thereby the interference in a cellular network.
It is another object of the present invention to provide a method and an apparatus that will enable the traffic load to be kept constant in a network, for example, for test purposes.
It is yet another object of the present invention to enable reliable measurements of network performance.
It is still another object of the present invention to provide a method and an apparatus that will enable the creation of heavy loads in the air interface in a mobile telecommunications network.
These objects are achieved by a method of controlling the traffic load in a telecommunications system in which the communication between terminals and the network takes place through an air interface, comprising the following steps:
determining an interference, that is, to be generated,
generating said interference in the network.
Preferably, the interference is generated by generating a traffic load in the air interface. The traffic load to be generated may be determined on the basis of the current traffic load or to keep the total traffic load at a constant level. Dummy traffic load may be added to the ordinary traffic load in dependence of the current ordinary traffic load.
The output power and/or the utilization of Downlink Discontinuous Transmission (DTX) of the generated dummy traffic may be controlled, for example, in dependence of the output power and DTX utilization of an occupied traffic channel.
An apparatus for carrying out the method is also disclosed, comprising
means for determining an interference to be generated,
means for generating said interference.
The apparatus may also comprise means for controlling the power and/or the utilization of DTX of the dummy traffic generated.
Creating a dummy traffic load means occupying one or more channels by transmitting useless information (xe2x80x9cdummy burstsxe2x80x9d) in these channels, that is, information that is neither payload nor control information.
The amount of dummy traffic to be generated may be determined in different ways:
The total load (dummy traffic and ordinary traffic together) may be kept at a constant level.
An amount of dummy traffic may be added in dependence of the amount of ordinary traffic, for example, a certain percentage may be added.
A constant amount of dummy traffic may be added.
The invention offers the following advantages:
The possibility to create a work load enables the performance of tests requiring high loads in low traffic areas or at times when the traffic load is low, such as the night time.
The possibility to keep the load in a system constant makes the tests and measurements performed in the systems more reliable.
The traffic generator enables network operators to predict the performance of the network for a given number of subscribers.